Science - Chemistry

Helium(He), Neon (Ne), Argon (Ar), Krypton(Kr) Xenon (Xe) and Radon (Rn).

• Group 0(sometimes called 8)
• Full outer shell
• Stable

Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), Caesium (Cs) and Francium (Fr).

• Group 1
• Soft
• Reactive
• React vigorously with water
• Become more reactive as you go down the group

Fluorine (F), Chlorine (Cl), Bromine(Br), Iodine (I) and Astatine (At).

• reactive non-metals
• darker as you go down the group
• reactivity decreases as you go down the group 
• boiling points increases as you go down the group

1

1

Negligible/ Nearly 0

+1

Neutral/ 0

-1

Nucleus

Neucleus

Energy shells around the Nucleus

Atomic mass unit

The number of protons

Electrons

• mass of nucleus
• (protons + neutrons)

No. neutrons = mass number - atomic number

They have an equal amount of protons and electrons

• Atoms of the same element that have different number of neutrons in their nucleus
• e.g.¹⁴₆C   ¹²₆C

False because they have the same number of electrons

• The average mass of all isotopes taking into account their relative abundance
• _{abundance - how much}

• Add up the relative atomic mass of each atom
• CO₂
• 12+2(16)

• a) 2
• b)8
• c)8

• Bonding between a Metal and a Non- metal
• The metal loses an electron and the non-metal gains it.
• Held together through electrostatic attraction.

• 
• Conduct electricity When molten or dissolved in Water
• Form an ionic lattice
• High melting and boiling points
• Hard to separate
• can decompose back to their elements

• 
• Bonding between two Non-metals
• They share electrons to achieve a noble gas state
• Held together by intermolecular forces

• Do not conduct electricity in any state
• Low melting and boiling point (even when the force is strong)
• Insoluble in water (may dissolve in other liquids)
• Liquid or gas at room temperature

• Regular arrangement e.g. a diamond
• High melting point
• Very hard
• Don't generally conduct electricity
• Insoluble in all liquids

• Hardest natural substance known on earth
• Shiny / sparkly
• very high melting point 3500°c +
• held together by strong covalent bonds
• each carbon has four bonds
• made entirely of carbon
• Does not conduct electricity because all the electrons are held together  between atoms

• Made entirely of carbon
• soft
• used in pencils
• has a layered structure
• held together by strong covalent bonds but with weak intermolecular forces allowing them to slide
• high melting point
• each carbon atom uses three of its bonds
• has delocalised electrons as only 3 are used in bonding
• can conduct electricity

• High melting point
• strong covalent bonds
• used in sandpaper
• each silicon atom makes four bonds to oxygen atoms

It can only be moulded once as it sets when it comes into contact with heat

Can be moulded many times as when it comes into contact with heat it melts

Melting range as they are not pure subatances

They have cross links that hold them in position

They are made under different conditions and have a different catalyst

Can change shape (soft / flexible)

Can stretch without snapping

When it is struck it will make a sound

They have free moving electrons (delocalised)

• Ductile 
• Sonorous
• malleable
• have high melting pints

• 
• Bonding between two metals
• Atoms become positively charged as the free electrons move away
• The sea of electrons mean the atoms are attracted

• Atomic mass of the element
• divided by
• atomic mass of compound
• then times 100
• e.g.
• % of Carbon in CO₂
• 12/44 x 100 = 27.27 %

The smallest, whole, number of atoms in a formula

• _element                   Al                               Cl
• Mass                      9g                           35.5g

_Ar                                   27                         35.5   

_Mass/Ar                27/9 = 0.33333...    35.5/35.5=1

• _/smallest         0.3../0.3...=1             1/0.3...=3
• _{empirical formula}        AlCl₃

• Draw a table with the number of elements +1 columns
• Draw 6 rows Labelled Element, Mass, Ar, Mass/Ar Mole ratio (/ smallest) and Empirical formula
• In the rows fill in the information
• Make sure the numbers that are created after /smallest are whole numbers
• if not times to make the smallest whole number (e.g. 1.5 and 2 times them both by 2 to get 3 and 4)
• write your numbers in the correct places after the right element and you have your empirical formula

• Ti + 0₂ → TiO₂
• 1 mole of .... is
• Ti = 48g O₂ =32g TiO₂ = 80g
• For Ti M=W/R = 3.4/48= 0.070833333... mol
• For TiO₂ We make 0.070833333 mol
• W=MxR = 0.07083333... x 80
• = 5.666...g

• CaCO₃ → CaO  + CO₂
• =100g        56g      44g
• 5.6 = 56/10
• 100/10= 10
• 10g of CaCO₃

• 2Mg + O₂ → 2MgO
• W=2g M=? R=24
• 2/24 =0.0833333..
• Molar ratio is 1:1 so 0.083333. mol of Mg makes 0.08333... of MgO
• W=MxR
• W= 0.08333.. x 40 = 3.3333...g

• 1.65/3.333333...  x100 = 49.5%
• 50%

Percentage yield = actual yield /theoretical yield x100

To separate different substances dissolved in a liquid

The sample is dissolved in a solvent, then injected into one end of the column.An unreactive gas - usually nitrogen - carries the sample through the column.Different substances in the sample travel through the column at different speeds and so become separated from each other.The separated substances leave the column one after the other. As they leave, they are detected by a detector.

The time taken for a substance to travel through the column

the number of compounds present in the sample

the retention time

A mass spectrometer is able to identify substances very quickly and accurately. It can detect very small amounts

this combined GC-MS method allows the separated substances leaving the column of the GC machine to be detected.

The mass spectrometer can be used to identify substances quickly and accurately, and in very small amounts. It can also provide the relative formula mass of the substances separated by gas chromatography. The peak furthest to the right in a mass spectrum is called the 'molecular ion peak'. Its relative mass is the relative formula mass of the substance being analysed.